BIOLOGY
CELL BIOLOGY:
Prokaryotic organisms are single celled eg. Bacteria cell.
Eukaryotic organisms are multi-cellular e.g. Plant and animal cells
Animal cells (sub cellular structures)
1)Nucleus = contains genetic material that controls activities of the cell
1)Mitochondria = Where aerobic respiration takes place, which transfers energy to the
cell
• Cytoplasm = where chemical reactions take place. Contains enzymes that control these
reactions
1)Cell membrane = Holds cell together and controls what goes in and out
• Ribosomes = where proteins are made (protein synthesis)
Plant cells
Plant cells have the same sub cellular structures as animal cells, but they also have:
▪ Cell wall - supports the cell and strengthens it
▪ Permanent vacuole - contains cell sap
▪ Chloroplasts - where photosynthesis occurs which makes food for the plant. Contain
chlorophyll which absorbs light.
Bacterial cells - much smaller
1)Cell membrane
2)Cell wall
3)circular strand of DNA
4)plasmid
5)cytoplasm
Microscopy
Electron microscopes have a higher magnification and resolution than light microscopes,
and let us see smaller things.This has enabled biologists to see and understand many more
sub cellular structures.
Magnification = image size / real size
To convert micrometers (µm) to millimetres (mm), divide by 1000!!
MICROSCOPY- PRACTICAL 1
,To prepare slide:
▪ Add a drop of water to the middle of clean slide
▪ Cut up an onion and separate it into layers
▪ Use tweezers to to peel off some epithelial tissue from the bottom of one of the layers
▪ Using the tweezers, place the epithelial tissue into the water on the slide
▪ Add a drop of iodine solution to highlight objects in a cell
▪ Stand a cover slip upright next to slide and carefully tilt down so it covers the slide. Try
not to trap air bubbles or it will obstruct view.
To use slide:
▪ Clip prepared slide onto the stage
▪ Select lowest-powered objective lens
▪ Use coarse adjustment knob to move stage up just below objective lens
▪ look down eyepiece. Use coarse adjustment knob to move stage downwards until image
is roughly in focus
▪ Adjust focus with fine adjustment knob until you get a clear image
Cell differentiation and specialisation
Differentiation is the process by which a cell changes to become specialised for its job
Most types of animal cell differentiate at an early stage.
Many types of plant cells retain the ability to differentiate throughout life
Undifferentiated cells are called stem cells.
Sperm cells are specialised for reproduction
Function = to get male DNA to female DNA
- Long tail and streamlined head to help it swim to egg
- Lots of mitochondria to provide energy
- Carries enzymes in its head to digest through egg cell membrane
Nerve cells are specialised for rapid signalling
Function = To carry electrical signals
- Long to cover more distance
- Branched connections at ends to connect to other nerve cells and form a network
Muscle cells are specialised for contraction
,Function = to contract quickly
- Long to have more room to contract
- Contain lots of mitochondria to generate energy for contraction
Root hair cells are specialised for absorbing water and minerals
- Long hairs that stick out to give a big surface area
Phloem and xylem cells are specialised for transporting substances
- Cells are joined end to end to form tubes to transport the substances
- Xylem cells are hollow in centre and phloem cells have very few sub cellular structures
so stuff can flow through
Stem cells
Stem cells are undifferentiated cells which can differentiate into any type of cell.
They are found in early human embryos or, in adults, bone marrow. In plants they are
found in the meristem
The bone marrow adult stem cells can only turn into blood cells.
Stem cells can be grown in a lab to produce clones (genetically identical cells) and made
to differentiate into specialised cells to use in medicine or research.
Medicine uses adult stem cells to cure disease - for example stem cells transferred from
bone marrow of a healthy person can replace faulty blood cells in the patient who receives
them.
Embryonic stem cells could also be used to replace faulty cells in sick people e.g. insulin
producing cells for diabetes, nerve cells for people paralysed by spinal injuries.
Therapeutic cloning - embryo made to have same genetic information as patient so stem
cells produced would have same genes and wouldn't be rejected by patients body.
Risks of using stem cells in medicine - stem cells grown in lab could become
contaminated with a virus which could be passed on to patient and make them sicker.
Stem cells in plants:
In plants stem cells are found in the meristems. The stem cells are then used to produce
clones of whole plants cheaply and quickly.
This means they can be used to grow plants of rare species to prevent them being wiped
out.
They can also be used to grow crops of identical plants that have desired features for
farmers eg. Disease resistance
For arguments of embryonic stem cells:
, + Curing people who already exist and are suffering is more important than rights of
embryos
+Embryos used are usually unwanted ones from fertility clinics which would have been
destroyed anyway
Against embryonic stem cells:
- Human embryos are potential human lives
- Scientists should concentrate more on finding and developing other sources of stem cells
so people could be helped without having to use embryos
Chromosomes and Mitosis
Nucleus contains genetic material in the form of a chromosome.
Chromosomes are coiled up lengths of DNA molecules
In a human body cell there are 23 pairs of chromosomes - 46 overall
Cell cycle - makes cells for growth, replacement and repair:
Multicellular organisms use mitosis to grow or replace cells that have been damaged
The end of the cell cycle results in two new cells identical to the original cell, with the
same number of chromosomes.
Stages:
▪ DNA replicates itself so there’s one copy for each new cell
▪ Chromosomes line up at centre of cell and cell fibres pull them apart. Two arms of each
chromosome go to opposite ends of the cell.
▪ Membranes form around each set of chromosomes. These become nuclei of each of the
two new cells
▪ Cytoplasm and cell membrane divide
▪ Cell has now produced two new daughter cells which are identical to the parent cells
Diffusion
Diffusion is the spreading out of particles from an area of high concentration to an area of
low concentration.
Some substances transported in and out of cells by diffusion are oxygen and carbon
dioxide in gas exchange, and of the waste product urea from cells into the blood plasma
for excretion in the kidney.
The bigger the concentration gradient, the faster the diffusion rate. (Because the particles
have more energy so move faster)
In cell membranes:
CELL BIOLOGY:
Prokaryotic organisms are single celled eg. Bacteria cell.
Eukaryotic organisms are multi-cellular e.g. Plant and animal cells
Animal cells (sub cellular structures)
1)Nucleus = contains genetic material that controls activities of the cell
1)Mitochondria = Where aerobic respiration takes place, which transfers energy to the
cell
• Cytoplasm = where chemical reactions take place. Contains enzymes that control these
reactions
1)Cell membrane = Holds cell together and controls what goes in and out
• Ribosomes = where proteins are made (protein synthesis)
Plant cells
Plant cells have the same sub cellular structures as animal cells, but they also have:
▪ Cell wall - supports the cell and strengthens it
▪ Permanent vacuole - contains cell sap
▪ Chloroplasts - where photosynthesis occurs which makes food for the plant. Contain
chlorophyll which absorbs light.
Bacterial cells - much smaller
1)Cell membrane
2)Cell wall
3)circular strand of DNA
4)plasmid
5)cytoplasm
Microscopy
Electron microscopes have a higher magnification and resolution than light microscopes,
and let us see smaller things.This has enabled biologists to see and understand many more
sub cellular structures.
Magnification = image size / real size
To convert micrometers (µm) to millimetres (mm), divide by 1000!!
MICROSCOPY- PRACTICAL 1
,To prepare slide:
▪ Add a drop of water to the middle of clean slide
▪ Cut up an onion and separate it into layers
▪ Use tweezers to to peel off some epithelial tissue from the bottom of one of the layers
▪ Using the tweezers, place the epithelial tissue into the water on the slide
▪ Add a drop of iodine solution to highlight objects in a cell
▪ Stand a cover slip upright next to slide and carefully tilt down so it covers the slide. Try
not to trap air bubbles or it will obstruct view.
To use slide:
▪ Clip prepared slide onto the stage
▪ Select lowest-powered objective lens
▪ Use coarse adjustment knob to move stage up just below objective lens
▪ look down eyepiece. Use coarse adjustment knob to move stage downwards until image
is roughly in focus
▪ Adjust focus with fine adjustment knob until you get a clear image
Cell differentiation and specialisation
Differentiation is the process by which a cell changes to become specialised for its job
Most types of animal cell differentiate at an early stage.
Many types of plant cells retain the ability to differentiate throughout life
Undifferentiated cells are called stem cells.
Sperm cells are specialised for reproduction
Function = to get male DNA to female DNA
- Long tail and streamlined head to help it swim to egg
- Lots of mitochondria to provide energy
- Carries enzymes in its head to digest through egg cell membrane
Nerve cells are specialised for rapid signalling
Function = To carry electrical signals
- Long to cover more distance
- Branched connections at ends to connect to other nerve cells and form a network
Muscle cells are specialised for contraction
,Function = to contract quickly
- Long to have more room to contract
- Contain lots of mitochondria to generate energy for contraction
Root hair cells are specialised for absorbing water and minerals
- Long hairs that stick out to give a big surface area
Phloem and xylem cells are specialised for transporting substances
- Cells are joined end to end to form tubes to transport the substances
- Xylem cells are hollow in centre and phloem cells have very few sub cellular structures
so stuff can flow through
Stem cells
Stem cells are undifferentiated cells which can differentiate into any type of cell.
They are found in early human embryos or, in adults, bone marrow. In plants they are
found in the meristem
The bone marrow adult stem cells can only turn into blood cells.
Stem cells can be grown in a lab to produce clones (genetically identical cells) and made
to differentiate into specialised cells to use in medicine or research.
Medicine uses adult stem cells to cure disease - for example stem cells transferred from
bone marrow of a healthy person can replace faulty blood cells in the patient who receives
them.
Embryonic stem cells could also be used to replace faulty cells in sick people e.g. insulin
producing cells for diabetes, nerve cells for people paralysed by spinal injuries.
Therapeutic cloning - embryo made to have same genetic information as patient so stem
cells produced would have same genes and wouldn't be rejected by patients body.
Risks of using stem cells in medicine - stem cells grown in lab could become
contaminated with a virus which could be passed on to patient and make them sicker.
Stem cells in plants:
In plants stem cells are found in the meristems. The stem cells are then used to produce
clones of whole plants cheaply and quickly.
This means they can be used to grow plants of rare species to prevent them being wiped
out.
They can also be used to grow crops of identical plants that have desired features for
farmers eg. Disease resistance
For arguments of embryonic stem cells:
, + Curing people who already exist and are suffering is more important than rights of
embryos
+Embryos used are usually unwanted ones from fertility clinics which would have been
destroyed anyway
Against embryonic stem cells:
- Human embryos are potential human lives
- Scientists should concentrate more on finding and developing other sources of stem cells
so people could be helped without having to use embryos
Chromosomes and Mitosis
Nucleus contains genetic material in the form of a chromosome.
Chromosomes are coiled up lengths of DNA molecules
In a human body cell there are 23 pairs of chromosomes - 46 overall
Cell cycle - makes cells for growth, replacement and repair:
Multicellular organisms use mitosis to grow or replace cells that have been damaged
The end of the cell cycle results in two new cells identical to the original cell, with the
same number of chromosomes.
Stages:
▪ DNA replicates itself so there’s one copy for each new cell
▪ Chromosomes line up at centre of cell and cell fibres pull them apart. Two arms of each
chromosome go to opposite ends of the cell.
▪ Membranes form around each set of chromosomes. These become nuclei of each of the
two new cells
▪ Cytoplasm and cell membrane divide
▪ Cell has now produced two new daughter cells which are identical to the parent cells
Diffusion
Diffusion is the spreading out of particles from an area of high concentration to an area of
low concentration.
Some substances transported in and out of cells by diffusion are oxygen and carbon
dioxide in gas exchange, and of the waste product urea from cells into the blood plasma
for excretion in the kidney.
The bigger the concentration gradient, the faster the diffusion rate. (Because the particles
have more energy so move faster)
In cell membranes:
